A large amount of information is now available on the cellular events of immune responses to various antigens. The principal objective in the work to be outlined is to use some of this information in the investigation of a more complex situation - the response of mice to the tissue phase larvae of a multicellular metazoan parasitic organism, Ascaris summ. We will determine the influence of thymus-derived cells (T cells) and various antibody classes on the maturation of the helminth from embryonated egg in the gut to larvae in the liver and lungs as well as the nature of the antibody and cellular response induced in the host by migrating larvae. Evidence for immunological (T and B-cell mediated) suppression and enhancement of larval development will be sought, one of the initial experiments being to examine the T-cell dependence of antibody responses to the larvae themselves, whole Ascaris body fluid antigens, more defined fractions of such antigen preparations, and contained haptens such as phosphoryl choline. Reaginic (IgE) antibodies and eosinophilia are two hallmarks of helminthiasis. A major effort will be expended on isolating mouse IgE as well as obtaining purified populations of circulating eosinophils. The eosinophil remains the least understood cell type in the blood stream and we will look for anti-Ascaris antibodies at the cell surface as well as any pharmacologically-active factors liberated after contact wth Ascaris antigen. In addition the Ascaris antigens themselves are becoming interesting as carriers for small haptens in basic studies on T-cell function. Various haptenated Ascaris antigens will be used in our ongoing studies of the "helper" and "suppressor" functions of T cells in antibody production. Mouse strain differences have been detected (based on the number of lung-larvae recovered after Ascaris infection), and this will be followed up by a search for relatively simple genetic control mechanisms.